1. Technical Field
The present invention relates to a light source device and an image display apparatus, and more particularly to a technology of a light source device having a plurality of light emission units.
2. Related Art
Recently, a solid light source used for the purpose of illumination has been developed and improved. A light source device including the solid light source has advantages such as preferable color rendition, long life, and immediate turning on and off. Thus, an image display apparatus such as projector including the solid light source as light source has been proposed. Currently, a technology of the light source device having the solid light source which performs automatic power control (APC) for controlling outputs is known (for example, see JP-A-6-309685 and JP-A-2002-267967). According to the technology proposed in JP-A-6-309685, a light receiving element is provided around a light emission window of a light source housing through which light emitted from a semiconductor laser is released in a structure including the semiconductor laser within the light source housing, and the output from the semiconductor laser is controlled according to the detection result from the light receiving element. According to the technology proposed in JP-A-2002-267967, lights sequentially emitted from a plurality of semiconductor lasers are detected by time-division system to control the outputs from the respective semiconductor lasers. By stabilizing the output from the light source device under the APC, a projector can display stable images having desired brightness.
For displaying images by using the solid light source currently developed, light is supplied using a plurality of light mission units in some cases so as to obtain a sufficient light amount. When the plural light emission units are collectively driven, it is preferable that the outputs from all the light emission units are collectively detected for the output control of the light source device. For example, when a part of light emitted from the plural light emission units is detected by using the technology disclosed in JP-A-6-309685, or when light from the plural light emission units is branched for detection, there is a possibility that light having intensity exceeding the detection limit of the light receiving element enters the light receiving element. When the light having intensity higher than the detection limit enters the light receiving element, the output is difficult to be kept constant. This problem becomes larger as the output of the solid light source increases. On the other hand, the technology disclosed in JP-A-2002-267967 does not successively detect the combined outputs from the respective light emission units. Thus, this technology is difficult to be employed by the structure including the plural light emission units. According to the known technologies, therefore, it is difficult to obtain a stable light amount in some cases when light is supplied from the plural light emission units.